Very high precision measurements of the solubility of gases in pure water at low pressures (subatmospheric) as a function of temperature are exceedingly useful in the development of model theories of hydrophobic interaction in biological systems. The present apparatus is capable of a precision of 0.04 to 0.07% in the mole fraction (or Henry's Law constant). Measurements are made at 5K intervals from 274 to 328K. The gasses to be studied are propane, n-butane, ethylene, and acetylene. The high precision data will be treated to obtain Henry's Law constant and the standard changes in the thermodynamic properties upon solution. Of particular interest is the change in heat capacity since this quantity is very sensitive to changes of the structure of liquid water. In addition, we will be continuing the development of a micro-flow gas solubility apparatus which is connected to a mini-computer. This apparatus works rapidly and uses only small quantities (10-20 cc) of liquids so it will be adaptable to determining gas solubilities in expensive biological fluids. The precision is estimated to be 2-3%. The results will be analyzed via scaled particle theory and other relevant theories, especially those related to hydrophobic interaction.